Power conversion device

Abstract

A first control unit outputs a closing-operation command signal to a first switch at a timing calculated based on either a first closing time or a second closing time, whichever is later. The first closing time is a time required for the first switch to transition to a closed state after the first control unit detects a first detection signal indicating that a voltage detected by a voltage detection unit exceeds a predetermined threshold value. The second closing time is a time required for a second switch to transition to a closed state after the first detection signal is detected by a second control unit. The second control unit outputs a closing-operation command signal to the second switch at a timing calculated based on a first time. This can suppress variations in an operating time between a plurality of switches.

The invention claimed is: 
     
       1. A power conversion device comprising:
 a first power-supply circuit unit including
 a first converter to convert an AC voltage supplied from a power supply to a DC voltage, 
 a first circuit unit in which a first switch and a first resistor are connected in parallel, 
 a first capacitor to smooth a DC voltage supplied through the first circuit unit, 
 a first inverter to convert a DC voltage smoothed by the first capacitor to an AC voltage, and 
 a first control unit to control an opening operation and a closing operation of the first switch; 
 
 a second power-supply circuit unit including
 a second converter to convert an AC voltage supplied from the power supply to a DC voltage, 
 a second circuit unit in which a second switch and a second resistor are connected in parallel, 
 a second capacitor to smooth a DC voltage supplied through the second circuit unit, 
 a second inverter to convert a DC voltage smoothed by the second capacitor to an AC voltage, and 
 a second control unit to control an opening operation and a closing operation of the second switch; and 
 
 a voltage detection unit to detect a voltage between ends of the first capacitor, or a voltage between ends of the second capacitor, wherein 
 a line, through which the first circuit unit and the first capacitor are connected, is connected to a line, through which the second circuit unit and the second capacitor are connected, and a line, through which the first converter and the first capacitor are connected, is connected to a line, through which the second converter and the second capacitor are connected, 
 the first control unit outputs a closing-operation command signal to the first switch based on either a first closing time or a second closing time, whichever is later, where the first closing time is a time required for the first switch to transition to a closed state after the first control unit detects a first detection signal indicating that a voltage detected by the voltage detection unit exceeds a predetermined threshold value, and the second closing time is a time required for the second switch to transition to a closed state after the first detection signal is detected by the second control unit, 
 the second control unit outputs a closing-operation command signal to the second switch based on either the first closing time or the second closing time, whichever is later, 
 the first control unit outputs an opening-operation command signal to the first switch based on either a first opening time or a second opening time, whichever is later, where the first opening time is a time required for the first switch to transition to an opened state after the first control unit detects a second detection signal indicating that a voltage detected by the voltage detection unit is below a predetermined threshold value, and the second opening time is a time required for the second switch to transition to an opened state after the second detection signal is detected by the second control unit, and 
 the second control unit outputs an opening-operation command signal to the second switch based on either the first opening time or the second opening time, whichever is later. 
 
     
     
       2. The power conversion device according to  claim 1 , wherein
 the first closing time is a total time of a first time required for the first detection signal to be detected by the first control unit, and a first transition time required for the first switch to transition to a closed state after receiving a closing-operation command signal from the first control unit, 
 the second closing time is a total time of a second time required for the first detection signal to be detected by the second control unit, and a second transition time required for the second switch to transition to a closed state after receiving a closing-operation command signal from the second control unit, 
 the first opening time is a total time of a third time required for the second detection signal to be detected by the first control unit, and a third transition time required for the first switch to transition to an opened state after receiving an opening-operation command signal from the first control unit, and 
 the second opening time is a total time of a fourth time required for the second detection signal to be detected by the second control unit, and a fourth transition time required for the second switch to transition to an opened state after receiving an opening-operation command signal from the second control unit. 
 
     
     
       3. The power conversion device according to  claim 1 , wherein
 when a voltage detected by the voltage detection unit exceeds the threshold value, the first control unit generates the first detection signal and outputs the first detection signal to the second control unit, and 
 when a voltage detected by the voltage detection unit is below a predetermined threshold value, the first control unit generates the second detection signal and outputs the second detection signal to the second control unit. 
 
     
     
       4. The power conversion device according to  claim 2 , wherein
 the first switch notifies the first control unit of the first transition time and the third transition time, and 
 the second switch notifies the second control unit of the second transition time and the fourth transition time.